Variable inductance control device



June 13, 1950 w. H. WANNAMAKER, .IR 2,511,608

VARIABLE INDUCTANCE CONTROL DEVICE Original Filed June 22, 1944 3 Sheets-Sheet 1 Y ATTORY.

June 13, 1950 w. H. wANNAMAKER, JR 2,511,603

VARIABLE INDUCTANCE CHTEQL DEVICE Original Filed June 22. H44 5 Sheets-Sheet 2 INVENTOR. WILLIAM H WANNAMAKER JR.

June 13, 1950 w. H. WANNAMAKER, JR 2,511,608

VARIABLE INDUCTANCE CONTROL DEVICE Original Filed June 22, 1944 3 Sheets-Sheet 3 13 FIG. 8

IN V EN TOR.

WILLIAM H.WANNAMAKER JR.

ATTO Y.

coil B. The other terminal of the coil B is connected to one terminal of the coil b and the connected coil terminals have a common ground connection I4. The second terminal of the coil b is connected to the control grid 4 by a condenser I5 and conductor I6. The conductor I8 is connected to the cathode 3 by a resistance II and conductor I8.

The conductor I8 also connects the cathode 3 to one terminal of a relay coil D. The latter has its second terminal connected to the supply conductor I by the conductor 8. The conductors I2 and I8 are connected by a condenser I9. The conductor I2 is also connected by a conductor 28 to the cathode 2l of the diode valve a. The plate 22 of that valve is connected through the conductor 9 to the alternating current supply conductor 2. electromagnetic relay DD which also includes a second relay coil DA. The latter has one terminal connected to the conductor 8 and has its second terminal connected through a resistance 23 to a movable switch member 24. In its full line position the switch member 24 is connected to the conductor 20 and thereby to the cathode 2I of the diode a. In its dotted-line position, the switch member 24 is connected to the conductor I8 and thereby to the cathode 3 of the tetrode a. The conductors 8 and 28 are connected by a condenser 28. The choke coil I8 is shunted by a resistance 2'I. The terminals of the coils B and b connected to the condensers I3 and I5, respectively, are advantageously connected by a resistance 28. The terminals of the coil D are connected by a condenser 29. The conductor I8 is connected to ground at 3| through a condenser 30.

The control system shown in Fig. 1 is operable in one or the other of two ways, accordingly as the switch 24 occupies its full-line position or its dotted-line position. In normal operation with the switch 24 in its full-line position a portion of the plate current flowing from supply conductor 2 through conductor 9, diode plate 22 and cathode 2 I, ows through the switch 24, resistance 23, relay winding DA and conductor 8 to the supply conductor I. Another portion of the diode plate current then flowing through conductor 9, plate 22 and cathode 2 I, passes through conductors 20 and I2, choke coil I8, conductor II, plate 6, cathode 3, conductor I8 and relay winding D to the conductor 8 and thence to the supply conductor I. The relay windings D and DA are so proportioned that with the switch 24 in its full-line position the relay DD is energized or deenergized, accordingly as the valve a is or is not oscillating. When the valve a is not oscillating the current flow through the coil D is sufficient to neutralize the opposing eiect of the current iiow through the coil DA and thereby deenergize the relay DD. When the valve A oscillates its space current diminishes and the relay DD is then energized by the greater current ow through coil DA.

. The armature D4 of the relay DD connects the terminal 33 to the terminal 34, or to the terminal V35 of a regulator E, accordingly as relay DD is deenergized or energized. The regulator E may described, and with the relay DD operatively energized only under the condition in which the regulator needs to transmit energy to the conductors 3'I, the control system will fail safely. That is to say, any operating defect which prevents the space current ow through the valve a from being large enough to operatively energize the relay DD, will prevent the regulator E from transmitting energy through the conductors 3'I.

When the switch 24 is in its dotted line position the relay coil sections D and DA are connected in parallel in the plate circuit of the valve a, and the branchcircuit then including the coil D, and the branch circuit including the coil DA and resistance 23 Aare so proportioned that the relay 'energizing effect of the coil D exceeds that The relay coil D forms part of an be of a known type receiving energy through energized and the armature D4 engages the termina-l 35, but not when armature D1 engages the i terminal 34. With the regulator E operating as of the coil DA, but not suciently to operatively energize the relay DD, except when the valve a is not oscillating so that the plate current of that valve is relatively large.

The condenser 28 connects the diode cathode 2i to the conductor 8 and thereby to the supply conductor I. This insures D. C. operation of the valve a, and thus contributes to operational stability. The relay DD is responsive to very small changes in the total current flow through its coils D and DA, and operates safely in case of tube or power-line failure with the switch 24 in either of its two operating conditions. This makes it practically possible, as is advantageous in some'cases, to energize and deenergize the relay DD on and as a result of changes in the mutual inductance of the control coils B and b`r without decreasing their mutual inductance sufficiently to cause the valve a to stop oscillating.

'Ihe resistor 28 insures substantially complete stability of the oscillator system and positively prevents the valve a, from oscillating when the vane C is fully interposed between the coils B and b. I have experimentally determined that the sensitivity of the response of a practical form of the control system shown in Fig. 1 to movement of the vane C is not affected by the use of the resistor 28 if the resistance of the latter is above 10,000 ohms. The degenerative eiect of the resistance 28 is especially desirable in the case of a multi-oscillator system which may be used for three-position control as shown in Fig. 8.

The resistance 2I increases the tolerances permissible in positioning the control coils B and b relative to one another and the vane C. Resistance 2'I reduces the ratio of inductance to resistance of the circuit including the choke coil I0 and this operates to limit the effective impedance of the circuit into which the anode 8 works to some value less than the value of the resistance 2I. Resistance 21 may desirably have a value of 3,000 ohms.

With its control coils B and b in the form of flat, closely spaced spirals, as illustrated in Figs. 2-7 and hereinafter described, the control system shown diagrammatically in Fig. l is characterized by its inherent simplicity, reliability and capacity for operation with high sensitivity. It is practically feasible to proportion and design such a system so that the tube A will be rendered oscillating or non-oscillating, by a movement of the portion of the edge of the vane C adjacent the common axis of the coils B and b, which is not greater than one-thousandth of an inch. By way of example, and not by way of limitation, it is noted that in one practical embodiment of the control system in Fig. l, the capacitances of the condensers I3 and I5 are 0.00005 and 0.00007 mfd.,

respectively; and thefcapacitancect :each: oifthe condenser's lI9 andn30 `is -10.001 mid., though Vthe capacitance value-of neither: is critical. The capacitance'of the vcondenser 29 is1201mfd- The capacitances of :the oondensers I Stand -I S-Withfthe capacitance vof the tube A-*andtheV distributed capacitances ofthe circuit elements .provide ythe capacitance in the series resonant circuit portionsof the system. The :condensers I3 .and I5 also serve as` blocking condensers preventing riskof injurious current flow through coils B and b, due to the normal -60 cycle', 1110-120 volt potential between thesupply conductors I and 2. The condensers I9 'and '30`fservef2as Icy-pass .condensers and their respectiveicapacitances are not critical asnoted above.

In Figs.' 2-7 I have lillustrated .an 'instrument I-Izof especially desirable form embcdyingv al control system of .the1form shown l-and embodying alrpreferred structural form ofthe :variable inductance device claimed herein. The vane CA ofthe instrument H isan arc shaped body oflsheet .metal lof good'conductivity such .as aluminum, copper or brass attached to a pivoted support 60. The latter is Amountedfon a, horizontal pivot kISI Ycarriedrby the mechanism casing v62 and is suitably counter-weighted to free the vanefrom gravitational Ibias. The inductancevcoils B and b are flat spirals .each mounted on an individual support 63 and comprising va few convolutions only.` As shown, eachcoilincludesl/g turns; but I have obtained good results with. as manyas 11 1/2 c onvolutions'in e'achcoil.- In the preferred form illustrated, the two suppcrtsfiare' counterparts, each being a plate-like 4body of insulating material deformed to-provide a circular v4boss;or"projection-d at one side 'about which the corresponding coil B or b is wound; The coil terminals extend throughV andare `anchored by cement 'in holes formed inathelsupport 63, and'in practice, the bodyof each of 'the coilsB and b is anchored to the corresponding support 63 by cement. One terminal of each coilpasses away from the corresponding coil supporti 63 .through a grommet 65 in :the ylatter. Thetwocoil supportsSS' are advantageouslyfconnected to form a'IsingleY mechanical funit .by aV metallic -eyelet or Vhub part E@ which .extends through a portion .of

each support displacedfrom its-bosses 64. As

shown, the unit includingv one coilBand one coil'b and their supports 631' is deta'chably securedby a-clamping screwfSsI/tothe.endiof a Apost'portion 9'of the'casingz'. Theinductance coil construction just described ismechanically ysimpleland relatively inexpensive,and permits the.-

coils B and Ab to be spaced 'accurately andin desirable relation to one another. For example, the distance ybetweenthe bosses B4 rnaybe onesixteenth of an inch. In consequence, a very small angular movement-ofthe thinsheet metal.

vane CA Vmay produce a-"relativelyllarge-change in the'mutual inductance off-the coils although Veach of the latter comprises but' a fewl turns for convolution's.

In the instrumentshown -in Fig. 2, the vane CA-Y 6 connected througha-lever'and link arrangement of known type to an arm 11 oscillating'in accordance with changes in the value of the controlling condition, As shown in Fig. 2, the arm 11 is connected to the freeend of a Bourdon tube,

18 which has its other end anchored to theinstrument casing and connected `to one end of a capillary tube'19 through which a variable controlling iluid pressure is transmitted to the Bourdon tube 18. In consequence, the arm 11 oscillates about the-axis of the Bourdon tube in the clockwise or counter-clockwise direction, as the pressure transmitted bythe capillary 18 respectively decreases or increases.

Theknown type of linkandlever arrangement through which the link 15 is adjusted longitudinally in accordance with angular adjustments of the armk 11, comprises a lever element journalled on a pivot BI carried by the instrument `casing and'having one arm connected by alink 82 to the'arm 1l. A second arm of the lever 80 is connected by a link 83 to one end of a oating lever 84. The other end of the noating lever 84 is pivotally connected by, a pivot 85'to a control -point adjusting element 86. The latter is pivotally mounted on a pivot pin 81 carried by the instrument casing. The element 89, may beangularly adjusted about the pivot B1 byV means including a spur gear 38 in mesh with av spur gear :portion 86 of the member'ili.V The spur gear 86 may be rotated vby gearing including an adjusting shaft `B9 journalled on the instrument casing andlshown as ,formed with a kerf in one end Yfor screw -drive adjustment. The end of the link 15 remoteirom the rocker arm 12 is pivotally connectedtothe floating lever 84 intermediate the ends of the latter. The member 8E includes an index arm Bil/which indicates on the rotating instrument chart SI the control point or value ywhich the instrument is intendedto maintain approximately constant. The actual value of that control condition is indicated andrecorded on thechart 9i by a pen 92 carried at the free vend of apen arm 93 mechanically connected to the lever 89 so as to turn about the'pivot 8l in accordance with changes in the value of the pressure transmitted bythe capillary 19.

The Bourdon spiral 18 may be connected through the capillary tube 19 to any controlling nuid pressure source. Thus, for examplethat source may be a fluid pressure thermometer bulb EA as shown in Fig. 2, and the instrument H may then be employed in such a control system as is shown diagrammatically in Fig. 1 to give the ivane CA oscillatory movements relative tothe coils B and b, on changes in the temperature of ther bulb EA.

Regardless of the origin of the controlling pressure transmitted by the capillary 19 to the Bourdon tube "i8,V on a decrease or increase in said pressure, the arm 11 operates through its lever andlinkv connection to the rocker arm 12 to turn thefvane CA respectively clockwise or counterclockwise about the pivot GI. The-exact angular position into which the vane CA must turn to interrupt the oscillation of thevalve a will obviously depend on various control system consta-nts. Ordinarily, however, it will be a positionr in `which the left-handV edge of the vane, as seen in Fig. 2 extendsthrough the space between the fbosses 6A `of 'the two coil supports Q63, along Aor near the rdotted line S5 ofFig. 2. The respective positions of the vane and coil supports 63 in which the left-hand edge of thevane isalongside i thet=dotted line `95 mayjbe. readily, adjusted by an -minals 34 and 35, respectively, of Fig. 1.

angular adjustment of the coil supports about the axis of the clamping screw 68. As previously indicated, changes in the relative positions of an inductance shield or vane and inductance coils of the general character shown in Figs. 2-7 may be so constructed and arranged that a movement of the edge of the vane CA in a direction transverse to the dotted line 95, as great as one thousandth of an inch will be sufficient to cause the Valve a to oscillate or to cease from oscillating.

With the pin and slot connection between the rocker arm ll and the vane CA shown in Fig. 2, the ratio of the angular movements of the vane to that of the rocker arm is relatively very large when the pin 73 is close to the pivot 6l and its movement is generally transverse to the plane including the axes of the pivots 6l and 'l0 and said ratio diminishes as the pin moves away from said pivot. Advantage or the pin and slot connection characteristic just mentioned may be taken to make the instrument especially sensitive to movement in the portion of its range of movement in which such sensitivity is especially important.

Generally, maximum sensitivity is desirable Iwhen the vane is in or near the position at which oscillation begins and stops. Y As shown, the instrument H includes a diierential relay DE which is operatively like the relay DD and comprises resilient switch contacts DB2, DE and DE3 corresponding operatively to the armature control element D4 and control ter- The contact DE2 is biased to engage the contact DEl but is moved out of engagement with that contact and into engagement with the contact DE3 by the armature DE4 as shown in Fig. 4, when the relay DE is energized.

In some cases, more than one pair of control coils similar in construction to the coils B and b shown in Figs. 2-7, are advantageously combined.

in a control system with a single controlling vane element. Several forms of such a control system are shown and described in my earlier application Ser. No. 541,575, and one of those control system forms is shown in Figs. 8 and 9 hereof.

Figs. 8 and 9 illustrate a three position control system in which two control system units each like the control system shown in Fig. l are combined with a single controlling vane element `and a single relay mechanism unit, in such manner that the oscillation of the valve a of one unit will be initiated and terminated by movement of the controlling vane element into and out of a position diierent from that into and out of which it moves to initiate and interrupt the oscillation of the valve a of the other unit.

In the form illustrated in Fig. 8, the two electronic tubes may be and are shown as identical with the previously described tube A, but to simplify the description, one of the tubes shown in Fig. 8 is designated A, and the other is designated AA. The tube A of Fig. 8 is shown as associated with control coils B and b and with a diierential relay -DD exactly as is the tube A -of Fig. 1. The valve AA is similarly associated with control coils and a differential relay which may be duplicates of those associated with the valve A, but for convenience of description the control coils associated with the tube AA are designated BB, and ;bb and the differential relay associated with the tube AA is designated DD. Except as above noted,

' parts shown in Fig. 8 are designated by the reference symbols which are used in Fig. 1 to designate equivalent parts.

To avoid risk of objectionable reaction whereby.

either of the circuit units shown in Fig. 8 may give rise to oscillation, or interfere Awith oscillation, in the other unit, I advantageously arrange the two units as shown so that oscillation in each unit can occur only during the half cycles of power-line voltage which alternate with the half cycles during which oscillation in the other unit can occur. To this end the anode 22 of the tube A of Fig. 8 is connected to the supply conductor 2, and the anode 22 yof the tube AA is connected to the supply conductor l, and the winding center tap of the relay DD is connected to the supply conductor I while the Winding center tap oi` the relay DD is connected to the supply conductor 2.

As shown in Figs. 8 and 9 the coils B and b are alongside of, but are laterally displaced from the coils BB and bb, and the cooperating vane element comprises two separate, spaced apart, but rigidly connected vane members CA and CC. The vane member CA is formed, mounted and associated with control coils B and b exactly as is the vane member CA shown in Figs. 3 and 4. The Vane member CC is a iiat metallic plate which may be similar in general shape to the member CA, and its plane is parallel to but laterally displaced from the plane of the member CA. The member CC is rigidly mounted on the same vane supporting member 8U on which the vane member CA is mounted. The coils BB and bb are carried by supports 63C which may be identical with the supports 63 for the coils B and b. As shown, the coil supports 63C are mounted on a short post 69C carried by the instrument casing 62C, and are secured in place by a clamping screw 618C. The mechanism casing 62C is provided at one end with sockets 62A and SAA for the tubes A and AA, and supports the relay elements DD and DD at its opposite end.

When the vane element shown in Fig. 9 is at the intended limit of its movement in the clockwise direction, the vane CA is interposed between the coils B and b. 'Ihat position of the vane element might be either its high position, 0r its 10W position, depending on the character of the control system in which the vane element is employed. As Will be apparent, an adjustment of of the arm 'l2 relative to the arm 'll will reverse the direction of the angular adjustment of the vanes CA and CC produced by a given longitudinal adjustment of the link l5.

With the particular vane element, control coil, tube and relay arrangement shown in Figs. 8 and 9 the high position of the vane element is that in which the vane CA is interposed between the coils B and b and the vane CC is interposed between the coils BB and bb, and each of the associated tubes A and AA is then in its non-oscillating condition. Movement of the vane element counter-clockwise about its pivot `5i from its high position into its neutral position leaves the vane CC interposed between the coils BB and bb, but moves the vane CA into a position in which it is no longer interposed between the coils B and b to the extent required to prevent them from having suilcient mutual inductance to set the tube A into oscillation. In Fig. 9, the vane element is in or near the angular position in which the yoscillation of the tube A will be initiated by a small turning movement of the vane element in the counter-clockwise direction. To reach its other end, or low, position and thereby initiate oscillation of the tube AA, the vane element shown in Fig. 9 must turn in the counter-clockwise direction through an angle somewhat greater than thirty degrees from the position in which oscillation of the tube A is initiated. That .angle measures the so-called neutral width, or range of controlling `quantity variation between its high and low values. and may be adjusted by loosening one or both of the screws 68 and 68C and angularly adjusting the coil supports 63 and 63C toward or away from one another. In normal operation, both tubes A and AA continue to oscillate after the vane element turns into its low position, until the vane element turns clockwise from its low position far enough to again interrupt oscillation of the tube AA.

As shown in Fig. 8, the armature contacts D20 and D21, actuated by the energization and deenergization of the relays DD and DD', respectively, are associated with stationary contacts so as to operatively connect an energizing contact EC to a low control terminal EL, or to a. high position control terminal EH, or to a neutral control terminal EN, accordingly as both relays are energized, or both are deenergized, or as relay DD' is deenergized while relay DD is energized. As will be readily apparent, the effect on the energization and deenergization of the relays DD and DD of Figs. 8 and 9 which is produced by the adjustment of the controlling vane element into its low, neutral and high positions, depends on the form and spatial relation of the controlling coils and vane element, and may be Varied as conditions make desirable.

As has already been made apparent the operating characteristics of the system shown in Figs. 8 and 9 may be materially altered by angular adjustment of one or each of the coil supports 63 and 63C about its supporting screw 68 or 68C.

While, in accordance with the provisions of the statutes, I have illustrated and described the best forms of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the forms of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. In a control structure, the combination with a pair of inductance coil units each comprising a coil support including two rigidly connected, juxtaposed walls and two coils mounted on the said walls of said support at opposite sides of a kerilike space transverse to the axes of said coils, means supporting said units with the axes of the coils of each unit parallel to the axes of the coils of the other unit, and a vane element movable in a direction transverse to said axes into and out of each of said spaces to thereby vary the mutual inductance of the coils of each unit.

2. In a control structure, the combination with a pair of inductance coil units comprising a coil support including two rigidly connected, juxtaposed walls and two coils mounted on the said walls of said support at opposite sides of a kerflike space transverse to the axes of said coils, means supporting said coil supports with the axes of the coils of each unit parallel to the axes of the coils of the other unit and with the coils of one unit adjustable relative to the oher in a direction transverse to said axes and a vane element movable transversely to said axes into and out of said spaces to thereby vary the mutual inductance of the coils.

3. A combination as specified in claim 1, ln which the kerf-like spaces of the two coil supports are displaced from one another in the direction of said axes, and in which said Vane element comprises two vane members displaced from one another to permit movement of one member into one and movement of the other member into the second of said spaces.

4. A combination as specified in claim 1 in which one of said coil supports is angularly adjustable about an axis parallel to and laterally displaced from the axes of the coils.

5. A combination as specified in claim 1 in which each of said coil supports is angularly adjustable about an axis laterally displaced from the axes of the coils.

6. In a control structure, the combination with a vane element movable along a predetermined path, an inductance coil unit comprising a coil support and two coils mounted on said support at opposite sides of a kerf-like space transverse to the axes of said coils and intersected by said path, and supporting means upon which said support is mounted for adjustment about an axis parallel to and laterally displaced from the axes of the coils to thereby adjust said coils into different positions along said path, and a portion external to said space.

7. In a control structure, the combination with an inductance coil unit comprising a coil support and two coils mounted on said support at opposite sides of a kerf-like space transverse to the axes of said coils, supporting means upon which said support is mounted for adjustment about an axis parallel to and laterally displaced from the axes of the coil, and a vane element movable in a direction transverse to said axes along a path including a portion within said space and a portion external to said space, the portions of said path respectively within and without said space being varied by the angular adjustment of said support about said axis.

WILLIAM H. WANNAMAKER, J R.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 804,250 Miller Nov. 14, 1905 1,295,691 Cahill Feb. 25, 1919 1,488,310 Birch-Field Mar. 25, 1924 1,564,555 Goldsmith Dec. 8, 1925 1,679,459 Willans et al Aug. 7, 1928 1,708,539 Goldsmith Apr. 9. 1929 

